Crankcase gas usually contains pollutants in the form of soot particles and/or oil mist.
EP 1273335 B1 describes such a known device for cleaning of crankcase gas. The centrifugal separator of the known device has a stationary housing which delimits within it a chamber in which the centrifuge rotor is arranged to rotate. The centrifugal separator is arranged to be fastened to the side of the combustion engine, and an external feed line is provided to lead crankcase gas from the engine to an inlet provided on the housing and communicating with the centrifuge rotor. During operation, the pollutants are separated from the crankcase gas by the rotating centrifuge rotor, and the housing has accordingly an outlet for the separated pollutants (oil and soot) and a gas outlet for the cleaned gas.
SE 529 409 C2 refers to a similar device for cleaning of crankcase gas. This centrifugal separator has a stationary housing which encloses the centrifuge rotor and which has an interface surface configured for direct mounting of the housing on a valve cover of the combustion engine. The interface surface is provided with a gas inlet which, via an aperture in the valve cover, communicates directly with the crankcase gas in a space defined by the valve cover. Such a configuration results in no need to provide an external crankcase gas feed line. The housing comprises also a gas outlet for the cleaned gas and a special gathering trough for the separated pollutants.
The prior art device has proved to be very effective for cleaning of polluted gas. Within the vehicle industry there are constantly increasing environmental requirements with a view to reducing emissions to the environment. The devices indicated above are traditionally used for cleaning of crankcase gas from large diesel engines. There is however a need to clean also crankcase gas from smaller combustion engines, e.g. diesel engines of the order of 5 to 9 liters or still smaller engines for passenger cars. At the same time, the automotive industry sets high requirements in terms of compact and cost-effective solutions exhibiting high performance.